allow '_' in sysnames
always allow '_' in sysnames
Add KDBUS_CMD_CONN_UPDATE

Implement a method to update the connection's attach_flags at runtime.
handle: consolidate alignment checks
use item-based approach for KDBUS_CMD_CONN_UPDATE
connection: silently ignore unsupported items
kerneldoc: update
drop '_from_user' in kdbus_cmd_policy_set_from_user
also attach connection name to the info query, not only the sent message
consolidate most memdup_user to handle.c
namespace: move __user stuff to handle.c
bus: move __user stuff to handle.c

bus
endpoint: move __user stuff to handle.c
handle: use kdbus_memdup_user for CMD_HELLO
test: fix return value

Now that the interfaces are unified, the test failed.
handle: kill some KDBUS_IS_ALIGNED8 that aren't needed anymore
handle: cleanups
fix some checkpatch warning on over-long lines
more trivial style issues

In particular, checkpatch.pl --strict says stuff like this:

CHECK: Prefer kzalloc(sizeof(*slice)...) over kzalloc(sizeof(struct kdbus_slice)...)
+	slice = kzalloc(sizeof(struct kdbus_slice), GFP_KERNEL);
util: rename kdbus_validate_nul to kdbus_item_validate_nul

... so the function can do the length calculation itself